In beam addressable information storage systems, of either optical or magneto-optical type, it is critically important that the information storage disk be very precisely oriented relative to the read/write head in the disk drive system. In general, this may be accomplished by clamping the central hub opening of the disk onto a precisely oriented disk spindle-drive which is provided with a centering cone to position the disk at the correct axis of rotation and with a drive chuck surface which is precision oriented to maintain the disk in the desired plane of rotation during the read/write function. Accordingly, provision must be made for a suitable clamping device to be operative after the disk is inserted to clamp the disk to the spindle-drive.
For optimum utilization of available space in a compactly designed disk drive system, it is desirable to provide insertion guide means which is adapted to receive the disk and hold it in its plane of insertion during the read/write function. With an arrangement of this type, the spindle-drive is translated axially into engagement with the disk after the cartridge reaches its final operative position. The clamp, located opposite the disk from the spindle-drive, then operates to clamp the disk to the drive chuck surface. Here again, conservation of space makes it desirable that the clamp mount be kept as close to the disk as possible during the loading process, preferably with no movement of the clamp mount in the disk axial direction.
To protect the storage disk from the effects of dust and fingerprints, it is well known to enclose the information storage disk in a protective shell or cartridge provided with a normally closed shutter that is automatically opened when the cartridge is loaded into the disk drive system so as to expose a segment of recording tracks to the read/write head through an access aperture formed in the cartridge. It is desirable that the shutter not be opened until at least that portion of the aperture exposing the recording tracks is within the disk drive system to insure that the disk is not accidentally touched by the user during insertion. However, because the disk clamp and read/write components are normally in close proximity to the surface of the disk, typically within 1-2 millimeters, and it is preferable not to move these components axially of the disk, even during cartridge insertion, it is necessary that the shutter be opened early enough during insertion to allow the clamp and read/write components to clear the shutter and nest within the disk access opening as the cartridge is being inserted.
It has been found that the conflict between the need to keep the shutter closed during the initial insertion of the cartridge and the need to open the shutter soon enough to clear the read/write components can be accommodated by a fast acting shutter opening mechanism. However, the geometry is such that it is necessary to move or retract the clamp device in order to clear the shutter. Once the shutter is opened, provision can then be made to reposition the clamp device into its normal operating position in axial alignment with the spindle-drive. Any mechanism used to move the disk clamp to accommodate the cartridge loading process must assure precise alignment and firm seating of the clamp in its final operative position, preferably without the use of costly precision parts.
In the case of a magneto-optical information storage disk drive system, the read/write components include an electromagnetic bias coil which also must be maintained in close proximity to the recording tracks of the disk. As with the read/write head and the disk clamp, this coil must also be nested within the disk access aperture of the cartridge and, as a consequence, it is desirable that the apparatus employed to position the disk clamp also be used to position the bias coil.
It is therefore an object of the present invention to provide disk clamp positioning apparatus for a compactly designed beam addressable information storage disk drive system.
It is another object of the invention to provide disk clamp positioning apparatus that precisely positions the disk clamp in axial alignment with a corresponding spindle-drive while at the same time allowing for delayed opening of a cartridge shutter during the cartridge loading operation. It is another object of the invention to provide disk clamp positioning apparatus that precisely positions and holds the disk clamp firmly in alignment with the spindle-drive without the need for costly precision parts.
It is yet another object of the invention to provide disk clamp positioning apparatus of the type described that also functions to position an electromagnetic bias coil in close poximity to the recording tracks of a magneto-optical information storage disk.